Popup window using Struts

I have a struts application. One of the JSP pages in that application (Say A.jsp) pops up another JSP page(C.jsp) using a javascript window.open() function. The same ActionForm and the Action class are associated with both these pages. But in the popup JSP page(C.jsp), I see that all the form attributes are getting nulled out when it opens up. The parent JSP(A.jsp) sends the request to the Action class which in turn runs some business logic and generates response data and sends the response back to B.jsp. B.jsp runs javascript function in its <body> tag and pops up C.jsp. A.jsp, B.jsp and C.jsp all use same actionmapping. But form attributes are empty only in C.jsp.

Yes, I agree that if the popup jsp gets generated using action class, the values would be populated. But I do not know how to make the actionforward to be a popup window.
So, this is what I tried. I am still using Javascript to open the popup window.

I am storing the values to be populated in the popup window in session and retrieving them in the C.jsp(popup window) and that seems to work.